For nearly six decades, Frank Welker has been the voice hiding behind one of animation’s most recognizable mystery-solvers, and now he has revealed his favorite episode. Since Scooby-Doo, Where Are You! first sent Fred Jones, Shaggy, Velma, Daphne, and their four-legged friend into haunted houses and suspicious-looking castles in 1969, Welker has been along for the ride. From Fred’s signature catchphrases to the franchise’s ever-growing collection of ghosts, ghouls, and villains, few people know the world of Scooby-Doo quite like him.

Now, after 57 years of chasing clues and unmasking troublemakers, the veteran voice actor is looking back at the franchise and revealing one mystery that holds a particularly special place for him.

Frank Welker has had no shortage of episodes to choose from. After all, Scooby-Doo was his first animated series, and he has voiced Fred since the character’s debut. He has also voiced Scooby himself since 2002, making his connection to the franchise even more unusual.

Speaking exclusively to PEOPLE, Welker revealed that one episode from the final season of Scooby-Doo and Guess Who? particularly stood out to him: Season 2, Episode 24, A Haunt of a Thousand Voices! The episode has a wonderfully meta setup, turning the franchise’s own voice cast into part of the mystery.

“So many to choose from but…one I particularly liked was in the last season we did, [Scooby-Doo and Guess Who?],” he said. 

In the story, the Mystery Inc. gang visits Welker’s fictional mansion, Pacific Palisades, complete with a private airstrip and recording studio, where they encounter the real actors behind their voices. Matt Lillard, Grey DeLisle, Katie Micucci, and Welker himself become part of the animated adventure.

“It was so wonderfully confusing we had no idea who was who and what was what,” Welker remembered the experience as delightfully chaotic in the conversation with PEOPLE.

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And while Welker is looking back at one of the franchise’s memorable mysteries, the Mystery Inc. gang is already gearing up to investigate a whole new chapter with Netflix.

The Mystery Inc. gang is not putting away the magnifying glasses anytime soon. Netflix has officially wrapped production on Scooby-Doo: Origins, its upcoming live-action reimagining of the iconic mystery-solving crew. The eight-episode series is set for a global release in 2027, although an exact premiere date has not yet been announced.

The new series goes back to the beginning, following Shaggy and Daphne during their final summer at camp as they stumble upon a lost Great Dane puppy who may have witnessed a supernatural murder. Velma and Freddy soon join the investigation, setting the group on the path toward becoming Mystery Inc.\

The young sleuths will be played by Tanner Hagen as Shaggy, McKenna Grace as Daphne, Abby Ryder Fortson as Velma, and Maxwell Jenkins as Fred. Adding another first for the franchise, Scooby will be played by a real Great Dane, rather than a fully animated or CGI creation.

So while Welker's favorite mystery looks back at the franchise's playful past, Scooby-Doo: Origins is preparing to take the gang all the way back to where the mystery began.

Mystery Inc.’s Origin Story Unveiled in New Live-Action 'Scooby-Doo' Series

Which is your favorite Scooby Doo episode? Let us know in the comments.